In a traditional LTE (Long Term Evolution) communication system as shown in FIG. 1, traffic (e.g. user plane data) originated from one user equipment (UE), e.g. UE1, goes through an eNB (evolved Node B) and GWs (GateWays) in an operator's network before reaching another UE, e.g. UE2. Uu is an interface between a UE and an eNB. Naturally, a user is charged when using service provided by the operator. Charging is a functional entity within the communication system.
In general term, there are two charging mechanisms in a communication network, i.e. online charging and offline charging.
In offline charging, the resource usage is reported from the network to the Billing Domain (BD) after the resource usage has occurred. It is a process where charging information for network resource usage is collected concurrently with that resource usage. The charging information is then passed through a chain of logical charging functions. At the end of this process, CDR (Charging Data Record) files are generated by the network, which are then transferred to the network operator's BD for the purpose of subscriber billing and/or inter-operator accounting (or additional functions, e.g. statistics, at the operator's discretion).
The BD typically comprises post-processing systems such as the operator's billing system or billing mediation device. In conclusion, offline charging is a mechanism where charging information does not affect, in real-time, the service rendered.
In online charging, a subscriber account, located in an Online Charging System (OCS), is queried prior to granting permission to use the requested network resource(s). It is a process where charging information for network resource usage is collected concurrently with that resource usage in the same fashion as in offline charging. However, authorization for the network resource usage must be obtained by the network prior to the actual resource usage to occur. This authorization is granted by the OCS upon request from the network. When receiving a network resource usage request, the network assembles the relevant charging information and generates a charging event towards the OCS in real-time. The OCS then returns an appropriate resource usage authorization. The resource usage authorization may be limited in its scope (e.g. volume of data or duration); therefore the authorization may have to be renewed from time to time as long as the user's network resource usage persists. Note that the charging information utilized in online charging is not necessarily identical to the charging information employed in offline charging. In summary, online charging is a mechanism where charging information can affect, in real-time, the service rendered and therefore a direct interaction of the charging mechanism with the control of network resource usage is required.
Moreover, offline and online charging may be performed simultaneously and independently for the same chargeable event.
In a proximity service scenario, communication may happen between UEs directly as shown in FIG. 2. An operator can move the data path (user plane) off the access and core networks to direct links between UEs, which is called “direct mode” data path. Alternatively, data path may be locally routed via a proximate eNB as depicted in FIG. 3. Such communication mode is called “local mode”.
In an envisaged scenario, Mary, owners of Store A and Restaurant A, B and C are subscribed to an operator service which allows them to use proximity service. There might be hundreds of other stores/restaurants with the capability of proximity service in the vicinity of Mary. When Mary walks into a neighbourhood of Store A, she may be notified of the proximity of Store A. Mary then may decide to look for a restaurant, and thus (e.g. following interaction with certain application of her UE) may be notified of the proximity of Restaurant A. Mary may not be notified of the proximity of other establishment not found of interest according to the application being used. After she starts walking towards Restaurant B, Mary may be notified of the proximity of Restaurant B, and also of Restaurant C.
In such scenario, UEs are using LTE spectrum for data transmission, it is therefore reasonable that the usage period may be considered in an operator billing system. In another situation, terminal-to-terminal communication, either directly or locally, may be used by operator to offload the traffic in their network when necessary. Thus, there is a need to seek certain means to charge the use of proximity service.